[PATCH][RFC] Avoid table lookup in isascii, isxdigit.

[Paul Eggert]

On 04/13/2013 09:18 AM, Rich Felker wrote:
> I'm not convinced the standard requires it.

You may be right; the standard is murky
in this area.  Still, it's annoying if clear
typos like 'isdigit ("")' aren't diagnosed.